The present invention is generally concerned with the structure of a driving bogie for a tractive unit having at least one driving motor mounted in the bogie and at least two driven axles with each axle having an axle gear rigidly connected with the bogie frame. More particularly, the axle gear of the bogie has a hollow shaft embracing the respective driving axle upon which it is mounted and a hollow Cardan shaft rigidly connects the hollow transmission shaft and the driving axle and/or a driving wheel through centering articulated couplings.
Devices of the type to which the present invention relates are generally known in the prior art, for example, German DAS No. 1,530,026. In the articulated couplings provided in the known bogie arrangement, the joints of the two articulated couplings are designed as spherical joints. Such articulated couplings are formulated by statics, that is, without bracing forces appearing in the axial or Cardanic movements of the two shafts relative to each other and the restoring forces result only from the Cardanic movement of the ball joints of the hinged levers.
In a coupling which has four hinged levers, e.g. a so-called multiple link coupling, there appear compulsive forces in a Cardanic movement of the shafts relative to each other which are held within minimum limits by the use of rubber ball joints due to the radial contractability of the latter. If the hinged levers are arranged on the circumference in the same direction as in the known arrangement, no compulsive force appears during an axial movement of one shaft relative to the other. However, minimum rotation of the shafts relative to each other takes place in an axial movement. Such centric articulated couplings are, therefore, preferably used where a great deal of axial mobility of the shafts relative to each other is desired. In a case of axial deflection, an axial force occurs in a torque transmission due to the inclined position of the hinged lever. That is, the Cardan shaft must be guided axially at least by one of the articulated couplings.
In the articulated coupling with equidirectionally arranged hinged levers, all the hinged levers are stressed for tension, or all are stressed for compression, in the transmission of torque, depending on the direction of rotation. In case of tensile stress on the hinged levers, there occurs a stabilizing effect relative to the axial forces appearing in an axial displacement of the shafts since the reaction to the center increases with increasing torque. In a compressive stress, however, the deflecting axial force increases with increasing axial movement. Due to this difference regarding the different directions of rotation, the critical speed behavior and the amplitudes vary for the axial movements.
It is, therefore, an object of the present invention to provide an improved articulated coupling for bogie devices of the type described above. The object of the invention is to provide such improvement in a way that good Cardanic and axial mobility is maintained with central guidance of the shafts relative to each other. Furthermore, as an additional property of the articulated coupling, no axial force appears in axial and Cardanic deflections, and the critical speed behavior in the axial direction remains essentially the same relative to both directions of rotation. Additionally, a reduction in cost in the manufacture of ball joints may be achieved as a result of the present invention.